Testing the skin of a patient for an allergic reaction to any of a variety of allergens is a known technique involving penetration of the allergen into a small area of the skin and subsequently visually observing the reaction, if any, of the skin to the allergen. Known procedures for applying the allergen include the scratch test, the prick test and the intradermal test. The scratch test is carried out by applying a few drops of the allergen to the skin and slightly abrading the skin by scratching at that location. The prick test is similar except that abrasion of the skin is effected by making a plurality of pricks with a sharp needle. The intradermal test is carried out by injecting the allergen into the skin.
U.S. patents relating to the introduction of biochemical substances into the skin include U.S. Pat. Nos. 2,304,817, to Grozin, 2,817,336, (and Re. 25,637), to Kravitz et al, 2,893,392, to Wagner et al, 3,062,212, to Kravitz et al, 3,072,122, to Rosenthal, 3,136,314, to Kravitz, 3,556,080, to Hein, 3,814,097, to Ganderton et al, 3,964,482 to Gerstel et al, and 4,304,241 to Brennan.